Abstract:

Bees pollinate approximately 1/3 of the food we eat. They pollinate all of our fruits, nuts, and vegetables. Honeybees contribute approximately $15 billion in pollination services to U.S. commercial agriculture annually. However, reliance on a single insect species, the honeybee, for the pollination of a huge portion of the human food supply can be dangerous. Indeed, this is especially true considering that honeybees are in decline from Colony Collapse Disorder (CCD), thus putting the global food supply at risk. Today, honeybee colonies are down by 40% compared to the 1970’s.

Over the past four years, the current study has examined the different native bee species in Georgia apple orchards. The mining bees (Family Andrenidae: Genus Andrena) show the greatest promise as a native bee that could replace or supplement the honeybee in early blooming crops (April- May) such as apples, blueberries, etc. Mason bees (Family Megachilidae; Genus Osmia) may also be important in Georgia agriculture when the apple bloom is particularly early (March or April) as seen in 2012 and 2013.

In the 2013 growing season (March-September), 5047 bees from 28 Genera were collected during the survey. The mining bees (58.2% of the sample) clearly dominated the samples taken in the apple orchards. There is little doubt that mining bees are the key native pollinators for early blooming commercial crops in Georgia. Native bee diversity and abundance were similar to previous years, perhaps even a little higher. Mason bee abundance (54 bees collected) was lower than the previous year, but still higher than in 2010 or 2011.

Habitat enrichments were created to boost the abundance of both of these target groups (mining bees and mason bees). Both types of habitat enrichments showed promising results.

Introduction

Honeybees contribute $14.6 billion in pollination services to U.S. commercial agriculture annually [1]. The yields of some crops decrease by more than 90% when honeybees are not present [2]. Reliance on a single insect species, the honeybee, for the pollination of over 1/3 of the human food supply can be dangerous [3]. Indeed, this is especially true considering that honeybees are in decline from Colony Collapse Disorder (CCD), thus putting the global food supply at risk. Today, honeybee colonies are down by 40% compared to colonies available in the 1970’s [4,5]. In 2007, CCD resulted in sharp declines in honeybees in at least 35 states, including Georgia. In the affected areas, 50% of beekeepers reported significant colony losses [6].

The reduced availability of honeybee colonies has increased food production costs and reduced potential crop yields. Most farmers are dependent on rented honeybee hives in order to ensure their crops are fully pollinated. The shortage of honeybee colonies has resulted in a rapid increase in the cost of renting honeybee hives. For example, the cost of renting a single honey bee colony used in almond pollination in California increased from $35 in the early 1990’s to $150 per colony in 2007 [6]. The potential loss or reduction of the honeybee can have a devastating effect on agricultural production. We need to develop alternative strategies that are less dependent on the use of the honeybee in order to ensure long-term sustainably of insect pollinated crops.

The best alternative to honeybees is the native bees already present in the local environment [7-11]. With nearly 3500 species in North America alone, the diversity of different forms, pollen-strategies, and behaviors of native bees provide a wide range of use for agricultural operations. It is estimated that native bees already annually contribute $3 billion to U.S. agriculture [12].

In addition, native bees may exhibit much greater pollination efficiency compared to honeybees [13]. For example in apple pollination, one female Osmia cornifrons is estimated to pollinate 2450 apple per day, compared to 80 apples per day by a honeybee [14].

Every region, even every crop, has its own characteristic group of native bee pollinators.

Data concerning regional make-ups of these native pollinator-guilds are severely lacking, which has led to our reliance on the European honeybee. In fact, across the continent, available information on native bees is spotty at best [15]. Therefore, research is needed to determine which native bees are present in a given region and how best to enrich the habitat (e.g. nesting areas) to increase target native bee populations.

Our studies have identified the mining bee, Andrena crataegi, and its close relatives, the Melandrena, as being the ideal native bee(s) for North Georgia apple production. Other excellent apple pollinating native bees identified were the carpenter bees, bumblebees, and mason bees. It is time to expand the study to the next step: to develop habitat enrichments and other strategies to increase the abundance of targeted native bees in commercial apple orchards.

By establishing a strong network of native bees in Georgia agriculture, we can make Georgia Agriculture more secure and sustainable. In addition, an increase in reliance on native bees means that farmers will spend less money on pollination services (e.g. renting honey bee hives) that will increase farmer profits and potentially reduce food costs for the general public.

Literature Cited

1. Morse R.A. and N.W. Calderone. The Value of Honey Bees as Pollinators of U.S. Crops in 2000. Bee Culture 128:1-15.

7. Kremen, C., N.M. Williams, and R.W. Thorp. 2002. Crop Pollination from Native Bees at Risk from Agricultural Intensification. Proceedings of the National Academy of Sciences of the United States of America 99 (26): 16812-16816.

15. National Academy of Science. 2007. Status of pollinators in North America. National Academies Press, Washington, DC.

Project objectives:

Main objective

The main objective of the study is to create habitat/nesting enrichments that will maximize the overall abundance of the previously identified target bee species (mining bees and mason bees). These nesting/habitat enrichment areas are hypothesized to increase the abundance of the targeted native bees already present in the orchard.

In order to boost the abundance of the main native bee target species, the mining bees (Andrena crataegi and other mining bee species), soil enrichments sites will be needed. These bees prefer patches of soil in which to dig tunnels for their habitat and a place to brood their young. At each orchard, four trenches (about 12 inches deep and 60inches long X 18 inches wide) will be excavated.

In order to boost the abundance of the secondary target bee species (mason bees), four special nesting boxes for the bees will be created within each plot. The center of the nesting box will contain a large section of about sixty tubes (varying from 6mm to 8 mm) or wooden boxes with 40-80 holes (8 mm diameter).

Secondary objective

The secondary objective is to continue the survey of the native bee pollinators for a fourth year within the apple orchards, with a focus placed specifically on the apple bloom periods.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.

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